1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing semiconductor devices.
2. Description of the Related Art
A conventional transfer molding method injects seal resin between upper and lower molds in which a semiconductor device is placed and a substrate thereof is clamped. A gate for resin injection is provided on a surface of the semiconductor device on which electrodes for interconnections are provided. This arrangement of the gate, however, requires a large substrate size.
FIGS. 1A and 1B relate to a semiconductor device with two Ball Grid Array (BGA) type packages and illustrate the lower one 1 of the two packages. The lower package has an interposer 2, electrode pads 3, a gate 4 for injecting resin and a resin sealing portion 5. The electrode pads 3 are used to make connections with external electrodes of the upper package. FIGS. 2A and 2B show another conventional package 11. The package 11 has an interposer 12, electrode pads 13, a gate 14 for resin injection, and a resin sealing portion 15. As to the package 1, a semiconductor device has an area that is located in a corner and corresponds to the gate 4, the area being plated with gold which has a poor adhesiveness to the seal resin. This gold plating is intended to allow easy removal of the gate 4 after seal resin molding. The area plated with gold does not allow electrode pads 3 for making electrical connections to be arranged therein and needs a large portion of the substrate for the gold-plated area. This prevents miniaturization of the semiconductor device.
A proposal directed to eliminating the above problems has been proposed in which a gate is provided on an upper surface of the seal resin. This proposal does not use the upper and lower molds but employs three molds, namely, an upper mold, an intermediate mold and a lower mold. The intermediate mold has a cavity for a molded body and a gate for resin injection. However, the structure of the proposed molds makes it difficult to remove the gate and runner resin that remain after molding. Particularly, there is a need to clean the inner wall of the gate each time molding is performed because the injection port is small.
In order to solve the above problem, a plate mold method as shown in FIGS. 3A through 3F has been proposed (Japanese Patent Application Publication No. 2004-193582, hereinafter referred to as Document 1). An apparatus 20 for manufacturing a semiconductor device has an upper mold 21, a lower mold 22, and a plate 25 in which a cavity 26 is formed. A substrate 27 on which a semiconductor chip (not shown) is mounded is placed in a substrate holding portion defined in an open state of the upper mold 21 and the lower mold 22. Next, the plate 25 is disposed between the upper mold 21 and the lower mold 22. Melted resin is supplied via a supply port 24 formed on the lower mold 22. The melted resin supplied via the supply port 24 is injected into the cavity 26 via a runner 23. The state in which the cavity 26 is filled with the resin is held for a few minutes in order to cure the resin. A sealing portion 28 is formed into the same shape as that of the cavity 26. Thereafter, the lower mold 22 is moved down to separate the molded body and the upper mold 21 from each other. Unnecessary resin 29 is removed and the plate 25 is taken away, so that the device with the semiconductor chip sealed with resin can be completed.
However, the conventional art disclosed in Document 1 has a disadvantage in that a gate residual 210 frequently results. When there is the gate residual 210, or resin burr, after removal of the unnecessary resin 29, the semiconductor device is thickened. Alternatively, if the gate is undercut, the semiconductor device may have an exposed portion.